We have collected steady-state laboratory data for over 2600 patients, age 2 years and over, with sickle cell anemia (HbSS), HbSC disease, and HbS-β⁺-thalassemia. The packed cell volume (PCV) is lower in males than in females until 17 or 18 years of age in HbSS and ages 13 to 15 in HbSC, but then becomes consistently higher in males. After age 40, the PCV falls in HbSS. The steady-state leukocyte count in HbSS is higher than that in normals, blunting the utility of this measurement in the assessment of infection. In HbSC and HbS-β⁺-thalassemia, the leukocyte counts are more often within the range of normal. Platelet counts in HbSS are often found to be above normal and show a downward trend with age. There is a progressive rise in creatinine with age. In HbSS, this rise begins at age 14 and may be accounted for by the increased muscle mass that occurs with puberty. The further deterioration of renal function in patients over 20 may be a result of the known adverse effects of sickle cell disease upon the kidney. Our data provide a basis to compare perturbations caused by intercurrent complications and new therapies, as well as to contrast with similar information from other populations of patients with sickle cell disease.